a-a a-b a-i aaa aab aai aan aao aar ab- aba abb abi abn abo abr ai- aia aib aii ain aio air an- ana anb ani ann ano anr aoa aob aoi aon aoo aor ar- ara arb ari arn aro arr baa bab bai ban bao bar bba bbb bbi bbn bbo bbr bi- bia bib bii bin bio bir bna bnb bni bnn bno bnr boa bob boi bon boo bor bra brb bri brn bro brr ia- iaa iab iai ian iao iar iba ibb ibi ibn ibo ibr iia iib iii iin iio iir in- ina inb ini inn ino inr io- ioa iob ioi ion ioo ior ir- ira irb iri irn iro irr n-i naa nab nai nan nao nar nba nbb nbi nbn nbo nbr nia nib nii nin nio nir nna nnb nni nnn nno no- noa nob noi non noo nor nra nrb nri nrn nro nrr o-i oaa oab oai oan oao oar ob- oba obb obi obn obo obr oia oib oii oin oio oir on- ona onb oni onn ono onr oo- ooa oob ooi oon ooo oor or- ora orb ori orn oro orr ra- raa rab rai ran rao rar rba rbb rbi rbn rbo rbr ria rib rii rin rio rir rna rnb rni rnn rno rnr roa rob roi ron roo ror rra rrb rri rrn rrr